GIS APPLICATIONS FOR KNOWLEDGE AND PRESERVATION OF HIERAPOLIS OF
PHRYGIA SITE.
A.Spanò (*), B. Astori(*), C. Bonfanti (*), F. Chiabrando (*)
(*)
DINSE, Politecnico di Torino, II Facoltà di Architettura, viale Mattioli 39 – 10125 Torino – Italy
antonia.spano,bruno.astori,cristina.bonfanti,filiberto.chiabrando@polito.it
KEYWORDS: GIS, Documentation, Archiving, Conservation, Surveying, Mapping, DBMS.
ABSTRACT
Lately, Geographic Information Systems are increasingly exploited in archaeological studies or, generally, in projects aimed to the
preservation of cultural heritage. Among the large number of reasons that make GIS a suitable tool to manage this kind of programs,
at once it’s possible to identify two main topics for this achievement.
The first one concerns the high capacities of GIS to enable advanced storage, representation and management of spatial data,
connecting them to collections of different nature data (archaeological, architectural, historical, etc.); these archives can be suitably
set and managed in several semantic levels with a spatial reference, overlaying topogaphic maps. The second order of reasons is
connected with present development of geographic mapping: the improvements in acquisition, processing, management and digital
representation metodologies request proper tools, in order to make new mapping products usable and widespread.
The recent growth of satellite images analyses and aerial photograms interpretation have in fact substantial role in cultural heritage
documentation, supporting objectives of modern Archaeology in spotting areas of probable location of archaeological sites or finds.
The designed GIS of Hierapolis, whose carrying out is going on, can based itself on a huge amount of metric data relating
monuments and diggings, collected during the last years thanks to topographic and photogrammetric surveys. Besides close range
surveys aimed to document architectural structures and ruins, always originating vectorial representation, a complete digital site map
at the urban scale 1:1000 has been accomplished.
The purpose to offer the chance of global data managing of city environment and architectural structures (scientists of different
disciplines register and store data covering the most diverse aspects of research) have to be founded upon very precise choices about
(geo)graphical database organization, mainly applied to proper arrangements of multiscale and multidisciplinary data.
This paper mostly presents our efforts and experiences to achieve this last object.
1. INTRODUCTION
For many years they used to produce ancient cities and
archaeological site plans in which buildings location were
represented along with their urban system into the point of view
of town planning.
Nowadays the most common trend is replacing archaeological
site plans with maps in which anthropic elements representation
doesn’t prevail over territorial ones, since there is a spreading
trend of analysing the signs of an ancient civilization and the
human organization in relation with the environment and the
territory on which they developed.
Since the representation of environment and its features is
increasingly felt as a need to study and interpret the human and
urban settlements, the GIS turn out to be the proper instruments
through which the different kinds of spatial data should be
managed and connected or compared to by other data having a
spatial reference. This kind of condition manifests itself in all
branches of study operating in an archaeological mission.
Another interesting reason about GIS is the fact that traditional
cartography, and often its corresponding vectorial products,
photograph a temporal static situation when an archaeological
site land, frequently subjected to fast transformations due to
excavations and restorations, needs a system of documentation
and representation which manages and ensures a continuous
flow of information (from the point of view of the updating
needs here the requests are many than in high urbanization
areas).
We can say that structuring this GIS the main features that have
been held into account could be sumarized in this way:
•
the multiscale trait of GIS, which is one of the most
important characteristics to satisfy the needs of study
ranging from the archaeological findings to the
architectonic structures and to the town and territory;
•
the second important feature is the peculiar organization
of the system arranged to aid a continuous updating of
spatial data (about new excavated areas, stratification of
metric information produced by excavations and
restorations, in short keeping traces of any trasformation)
This last aspect is supported by the realization of a relational
database (based on serverDBMS) archiving data about
topographic points and their landmarks on earth. This archive,
on one side, ensures the possibility to use the plano-altimetric
known coordinates of a great amount of points distributed on
the territory of the city to working groups of each branches for
detailed surveys, and, on the other side, the relational database
structure and its continuous implementation, constitute a first
step for a future retrieval of spatial information and other data
collections in the World Wide Web.
2. DATA ORGANIZATION
One of the basic concepts used to plan the GIS is the
consciousness that the reading capability and data
thematization, and, moreover, the interrogation and institution
of relationships between different classes, depend on primary
data organization: it means that the real system ability to
develop complex and advanced analysis and data managements,
is entirely due to the primary structuring of arrangement.
At the moment the multiscale organization of the global system
is mostly evidenced by the presence of spatial datasets at
different scale; quality control procedures according to spatial
data quality evaluation components, are used to validate data.
Next step of project will be the fulfilment of a multiusers GIS
which could allow to gain access to a map server, enabling
retrieval of spatial information and other nature data; this is the
reason why we chose to organize datasets into a geodatabase
format, which, at the moment is configurated as a simple
datasets collection with closely linked attributes.
As one of the most important things to use spatial data correctly
is knowing their nature, characters, boundaries in which to use
them, etc., an access database having quite a simplified scheme
of metadata has been devised; knowing data about data is a
necessary condition in order to permit to any operative unit
working at the archaeological Mission to access to spatial data
and to use them consciously.
for the excavated streets); it has the main role to associate
historical-architectonic and archaeological information in any
format and photographic documentation of each building to a
single identification code, and also the function to visualize and
effectively point out the presence of the ancient structure.
(Fig. 3)
The terrain objects are grouped in lines and polygons classes;
there are the edges and the boundaries of slopes and also of
excavated areas but great attention has been dedicated to the
limestone trenches which are a clear sign of the water
overrunning on the urban area, at first in a regulated way and
then, as a sign of the city decadence, in a frean uncontrolled
stream (Pamukkale is the theatre of one of the greatest natural
2.1 Spatial database of the city of Hierapolis
The spatial database of the ancient city of Hierapolis is mainly
built in agreement with standards set for largest scale numeric
cartography, meanwhile showing the evident specificities
related to the requirements of an archaeological site. For
example, the data grouping regarding territorial and anthropical
elements has peculiar reasons within archaeological sites where,
no doubt, the updating needs are marked by time in a different
way; this aspect is more emphasized because the generation
processes of these two data types are completely different on the
map of Hierapolis.
The map of Hierapolis was born by an integration of a 1:1000
scale plan built through a topographical survey and, moreover,
that land features have been extracted from a traditional map
(taken over by dated photograms) first rasterized and then
vectorialized (Spanò, 2002; Astori, Spanò, 2003); these two
elements provided together are the information which the users
learns from the first metadata form describing map.
This form includes a list of data types come together in the map;
highlighting their lineage heterogeneity (adding to the previous
data types, users have to know that a small number of ancient
building plans have been vectorized from traditional surveys,
and than registration processes based on control points
constraints led their positional accuraty to tolerance range.)
Outstanding important to the users is the main information
about the reference system: every user, (geologists,
archaeologists and all other researchers) usually need to know if
map is referenced or not to national cartography reference
system.
Figure 1 shows an hardcopy sheet of site map and a mask of
metadata database: while the first one, as usual, refer
schematically the definition of local and geographic reference
system, for planimetric and altimetric data, the second one is
much more richer, showing to users also details concerning
elaboration process of map.
Even datasets metadata scheme has been simplified in
comparison with standards; lineage, positional accuracy,
temporal accuracy and tematic consistency have been endowed
upon other parameters. It is a central aspect in such GIS a
proper updating of these metadata parameters concerning
buildings, ruins and diggings datasets.
Afterwards we try to synthesize main topics about cartografic
items organization, highlighting the geometric object type of
corresponding to datasets (points, lines, polygons).
A dataset of lines and one of polygons have been arranged to
group ancient city elements; the former means to represent and
communicate the basic planimetric structure of ancient
buildings whose thematization recalls the generical temporal
periodization of the city suggested by the founder of the Italian
Mission (Verzone 1977). (Fig. 2)
On the other hand polygons dataset contains objects which
coincide with the buildings profiles at earth level (it is the same
Figure 1. Comparison between essential metadata provided in
sheet legend and deeper information included in map
description metadata form. In the bottom the enlargement of
GPS general network and a planimetric accuracy control
scheme of the referencing of altimetric data to GPS network.
Figure 2. An example of ancient city dataset thematization in a
zoom-in view of digital map, spotting the Agorà.
Figure 5. The Necropolis vector data overlaying rasterized and
georeferenced Turkish map sheets. The rich presence of
elevation points is a useful dataset stored in GIS.
.
Figure 3: HTML pages are linked to objects representing
buildings to visualize catalogues of images 1
Figure 6. This selection by attributes highlights contours subset
deriving from elevation points of rasterized sheets; points have
been vectorized in a part of the map where there were lack of
altimetric informations.
Figure 4: Limestone trenches in the western area of the city.
events in the world, the formation of limestone basins; even in
the ancient time the city of Hierapolis was presumably very rich
in water and trying to walk along its distribution today could
add new information to reconstruct the city history).
About altimetry, all contours vectorized from Turkish map, has
been arranged in a dataset; moreover a point objects dataset
comprise altimetric points measured with various topographical
1
Photos acquired from aerostatic ballon. Cassanelli (University
of Pisa), 1997
methods. This last layer contains all the plano-altimetric points
belonging to three orders of networks (the main network
measured with GPS survey, the second order networks and a
third connection network between the two previous ones).
Secondly, another large set of plano-altimetric points comprises
the ground control points used to weld terrain relief data,
belonging to Turkish map and measured by topographical
intersections, to the GPS network. Finally numerous points
measured by detailed surveys are included because their
elevation is considerable in relationship with ancient structures.
Obviously, attributes concerning different measurement
metodologies and than points value, enable to perform
thematization or any kind of query to select them.
A layers group contains all the Turkish map rasterized sheets;
the raster format of this map at the scale 1:500 has been
subordinated to warping processing to recover the irregular and
Figure 7. The whole digital map displaying a possible visualization.
strong original deformation due to wrong reproduction; their
georeferencing has been possible thank to a very accurate
recognition aimed to discover their marks on terrain and to the
above-mentioned topographical intersections.
One of the functions of raster data is the documentation of some
elements existing in the past, as the hotels occupying some
areas of the site and now destroyed; another important role is
the ability to provide altimetric data through dense
aerophotogrammetrical elevation points which constitute an
important and useful archive in case of need. (Fig 5)
Another important layer is the TIN, generated by contours; the
jointly thematisms of each dataset produce a final visualization
observable in the image of Figure 7.
2.2 TIN creation and 3D visualization
One of the main effects of innovation in cartography, that has
led to the development of digital mapping, has been the
advanced use of altimetric data; the natural consequence has
been an increasing request and production of 3D mapping.
TIN creating is a very important topic within the actual
researches in Geomathics, primary for the high requirements of
three-dimensional reconstruction of land surface; but it also is
important to perform advanced spatial analysis employing
altimetric data, which can assume different shapes (vectorial
formats: surface, dtm, contours; or raster formats:
elevationgrid, slopgrid).
The TIN creation of central territory of Hierapolis has been
realized using contours; polygons of ancient buildings and ruins
and land natural objects have been used as the break-lines.
The TIN west limit, towards the declivity of the limestone
basins, has been intentionally interrupted on the last contour
available at 1:1000 scale, while the lack of informations
interrupts the TIN in the other directions.
Figure 8 (a,b) 3D scenes showing volumetric
relationship between theatre structures and hill slope.
Generally, modelling ancient buildings or their ruins require
more articulated needs in comparison with the usual extrusion
of the outline of built up areas in 3D urban cartography;
thinking to the important valences of the representation of the
reconstructive hypotheses concerning buildings, a suitable
ancient city modelling would have developed using a more
appropriate environment software (CAD). Anyway, a schematic
volume modelling of the buildings in a Geographic Information
System can highlight the relationship between built up
structures and land. We propose an exemplification considering
the theatres of the city: the theatre of Flavian age, under
restoration in the last 30 years of Mission activities, and the
more ancient hellenistic one.
Figure 8 emphasizes the deep difference between roman and
ellenistic theatres: while the more ancient ones take more
advantages by peculiar terrain orography, the roman building
tecniques evolution lead to the use of impressive retaining
walls.
3 MAP UPDATING, MULTISCALE GIS AND
TOPOGRAPHIC POINTS DATABASE.
We have just suggested that topographic points relational
database is related to map updating and to the plannig of next
Web GIS configuration
Before explaining archive structure we want to expound the
reasons why we decided to start from topographic data as the
ones to assign first to web sharing (it would be a sharing limited
to italian mission working groups).
Archaeological and architectural survey demand critical reading
of building structures; they need also a wide acquiring and
suitable collecting of tematic and metric data that will come
together in the final representation performing a very closed
integration. Then final representation is a result of objective
data and detailed interpretation of the object of interest that also
become graphical elements; this knowledge process is set at a
very large scale, 1:20÷1:100
Contemporary it is necessary to use a smaller analysis scale to
read and than visualize and comunicate the relations between
case study and the environment where it lies.
The city vector plan, that has been accomplished before the site
map and that has become a main part of it, arise mostly from
large scale acquisition processes applied on monumental
remainigs and diggings. A great deal of a low order of total
station traverses were set to encompass buildings, excavation
areas or other areas of interest, these networks, largely spread
on ancient city territory, have the role to base topographic
detailed surveys on architectural structures and ruins.
If updating of urban maps generally need aerophotogrammetric
flies every 5-10 years, in a archaeological site it is interestbearing to perform updating deriving them from large scale
surveys, that are produced in any case.
Stratigraphic survey is the typical operative approach of modern
Archaeology and it requires a continual assistance by
topographic measurements. Since in Hierapolis every working
group manages its own detailed surveys, the chance to
implement a relational database, storing data useful for
searching points on terrain and for using known coordinates,
become clear.
After carrying out large scale surveys, typical topographic
measures and processes, together with accuracy data control
procedures evaluating nominal scale change, enable to achieve
data integration in general map.
MySQL is the DataBaseManagementSystem used to manage
data storage, while data entry web interface is based on PHP
language
For istance, if in a certain city sector a new digging opening is
decided, measurements operators will look points up in
geodatabase graphic interface. If they find any, the server
database connection will allow access to data, regarding precise
location, precision index of points coordinates, etc.. The query
result is a set of alphanumeric and photographic data visualized
in a HTML page. (Fig. 9a)
Another important utility is the chance to select topographic
points with criteria connected with their location which is
obviously a typical ability of GIS. Many points are located on
ancient structures, and a considerable number of them are
located in buildings corners. The first topographic points feature
is selectable through a typical selection by location while the
second one is an esplicit attribute that data entry mask interface
require to fill. (Fig. 9 b-c)
This selection of selection raise to a remarkable role: if the
registration of aerial or satellite images is needed, selected
points can be used as high precision ground control points, to be
managed in warping tecniques.
4. PERSPECTIVES
One of the most important perspective of developement is the
systematics organization of data concerning each building and
excavation area. The implementation of spatial datasets
characterized by a larger nominal scale in comparison with the
datasets which costitute the 1:1000 map, is easily reliable such
as the forced visualization among a fixed range scale.
Figure 9. (a) Main topographic points query. (b) Data entry
mask, with building corner attribute highlighed. (c)
Topographic points over buildings spatial query.
(a)
(b)
(c)
Figure 10. Different limestone trenches spatial distribution in
diverse city areas.
whole city areas, sometimes coming after contours and
sometimes approssimatively following streets net.
Trenches vectorial dataset, overlaying slopegrid, derived from
TIN, are the imput data to establish, through spatial anlysis, a
possible setting of water flow.
In a similar way, we expect that another application, using
streets vector dataset and elevationgrid, will be able to provide
some data about possible connection between roads width and
their directions (West-East climbing the hill, North-South
coming after contours).
5. REFERENCES
Billen R., 2000. Introduction of 3D information in urban GIS: a
conceptual view, XIX ISPRS Congress, International Archives
of Photogrammetry and Remote Sensing , Amsterdam, The
Netherlands,
D’andria F. (a cura di), 1997, Metodologie di catalogazione dei
beni archeologici, Beni archeologici – Conoscenza e
Tecnologie, quaderno 1.1, Lecce Bari.
D’andria F. Semeraro G., 2003. Applicazioni GIS alla ricerca
archeologica. Modelli di formalizzazione dei dati, in I modelli
nella ricerca archeologica, Accademia Nazionale dei Lincei,
Roma.
(a)
De Bernardi Ferrero D. (a cura di), 2002. Hierapolis scavi e
ricerche IV– Saggi in onore di Paolo Verzone, Giorgio
Bretschneider editore, Roma.
Pamukkale National Park: Master Plan for Protection and Use
by Project Team, Ankara, 1969.
Spalla A., 2003. La dimensione tempo nella cartografia e nei
rilevamenti terrestri, invited relation to 7° National Conference
ASITA, Verona.
Spanò A., Astori B., Bonora V., Integrated and multiscale
spatial data to base a GIS for the ancient city of Hierapolis in
Phrygia, proceedings of ISPRS international workshop,
Ancona, 2003
(b)
Figure 11. Slopegrid (a) and elevationgrid (b) are raster data
useful for further advanced spatial analyses: they will be
exploited to study water flow and aspests related to hills relief
of streets net.
The interesting and deeper work we desire to develop on
datasets at 1:100 scale and larger, is to choose geometric type
classes to assign to dataset features (point, lines, polygons), in
order to effectively connect existing relational database,
regarding archaeological data of digging documentation or the
analysis and the interpretation of collapsed walls. (D’Andria
1997, D’Andria 2003).
At the end of this first project phase, GIS managing shows that
a considerable range of utilities can be directed to favour and
strengthen Conservation and Valorization of archaeological site.
Such map can improve potentialities of more linked works
among different research branches; digital map also constitute
the basic tool for proper design of tourist routes crossing the
site, which will be probably set soon.
At the moment we are working on two types of spatial analyses
that probable will give a contribution to some investigation
sector of general researche on the site. The first one concerns
the study of spatial distribution of limestone trenches crossing
.Spanò A, Le ragioni dell’intervento di natura topografica a
Hierapolis - 1999, in Hierapolis scavi e ricerche – Saggi in
onore di Paolo Verzone, Roma, 2002
Verzone P., L’urbanistica di Hierapolis di Frigia. Tracciato
viario e monumenti rimessi alla luce dal 1957 al 1972, in
L’Architettura in Grecia, Atti del XVI Congresso di Storia
dell’Architettura, Atene, 1977, pp. 402-413.
6.ACKNOWLEDGEMENTS
This work has been developed with the project “Hierapolis of
Phrygia:
archaeological
excavation
and
restoration
metodologies” financed by Italian Ministry of University and
Research in 2001. (National Coordinator: G. Ciotta;
Responsible of local unit: B. Astori)
Turkish traditional map has been provided by Turkish Ministry
of Culture through the interest of Francesco D’Andria, director
of the Italian Archaeological Mission.